Fruit Wheat ... gone wrong?

Another reason to fear girls' nights out (other than the shopping) - they talk about your beer and make specific requests. So I came home to find that SWMBO will be inviting her girlfriends over, and Sharon requested that I try to clone a rosé beer. I was utterly confused for a while, until she described it as a pink-coloured, sweet beer. Turns out she was referring to Witterkerke's Rose Beer, essentially a wheat beer infused with raspberries. This beer is hardly the pinnacle of manliness, but I rose to the challenge anyway (pun intended).

First thing we did was to obtain a bottle of Witterkerke's for a taste, to see what we're up against. Oh my #%@$&^ Beer Saint ... let me redirect you to some of  other people's thoughts. It's more like a cooler, than a beer. Oh well, a promise is a promise.

So on 27 May I got down to brewing a 10 gallon batch, with the idea of at least reserving 5 gallons of it being a normal wheat beer. As my last Belgian Wit attempt was as good as I wished it, I decided to use that base recipe. Alas!! I ran out of Wyeast 3944 Belgian Wit yeast, and only had WLP300 wheat yeast on hand. That's fine. So after an entire day of good work (brewing is still enjoyable nonetheless, girly beer or not), I finally put the 2 fermenters into the fermentation chamber.

10 gallon mash - fills my tun right up to the brim!

A week later, gravity had stabilised and I excitedly went for a sneak taste. Oh my #%@$&^ Beer Saint ... A cloud of sulphur enveloped me the moment I opened the chamber, heralding the Armageddon that was to come later. Smell - definitely sulphurous. With just that hint of green apple. Taste - definitely acid. And I could taste the sulphur.

What went wrong? I could think of a few possibilities:
1) Stressed yeast
I know I underpitched the yeast by almost half. And WLP300 is known to put our sulphur, especially when stressed.
2) Infection
I can't rule out a lactobacillus infection either, although I don't see any suspicious growths or pellicle formation.
3) Change in grist
OK, I admit it. I did change the recipe a bit. Instead of using flaked wheat, I used raw white wheat instead. I doubt however that this was the cause of the sour taste and sulphur. If anything, it'd cause low attenuation, which didn't happen.
4) Low fermentation temperature
I fermented at 20C, which is the lower end for WLP300. This should change more of the clove/banana phenolic balance, rather than cause sourness per se.

In a bid to salvage the beer, I just raised the temperature to 22C today. Hopefully, the yeast will be roused back into conditioning the beer and absorb the acetyldehyde (if it really is acetyldehyde - if it's acetic acid, I'm pretty much screwed). In addition, I'm hoping that the higher temp will precipitate out CO2 and bring the sulphur out of solution. Better in the air than in the beer.

I also added 100g of dried hibiscus as planned, to colour and flavour the beer - perhaps it could mask some of these faults? Either that, or I'm well on my way to creating a Franken-Beer.

Keeping my fingers crossed!

Update:
Actually the ladies really enjoyed the beer! it was sweet, intentionally overcarbed, and PINK! So yeah. I guess they love drinking malt cocktails, since they actually polished off the whole batch of that stuff!