Oh, OK, I get it now. Well, all right, but it might possibly have been better to post the question in the AquariumPlantFoodUK sub-forum.
In any case, this is all a bit strange and I reckon we need more data because the original post and subsequent information were a bit cryptic.
So, SJL, please help us out here. I do not have my Magneto/X-Men Mind Reading Helmet with me today. Does the story go like; I was using flourish micronutrient + Excel and everything was going fine for months, and then I switched to APF all-in-one + Excel and suddenly my plants started to melt? I apologize but this is completely unclear. Cause and effect have very specific relationships, so we need more details because your problems could possibly be completely unrelated to APF all-in-one. As I mentioned, this sounds like translucency and leaf dropping, which is CO2 related. Usually I'm bashing people for using too much light, but 30 watts T8 over a 45G is not unreasonable. Were the plants growing OK when using the combination of flourish micronutrient + Excel with this lighting level or were they already in decline by the time you switched to APF all-in-one?
Sorry if this seems like an interrogation at, but I'm just not getting a full picture here. Could you clarify?
Cheers,