A few drops of Ehrlich should be just fine, I think it was more likely the small amount of blotter you tested rather than too much reagent. I’ve had an 1/8 of a blotter sit in reagent for 15 minutes with no noticeable reaction, added another 1/8 and had a reaction soon after.
The purple colour is a good sign, although testing with a reagent is reductive rather than conclusive… for a definitive result you could send a tab into
Energy Control which would give you an idea of the dosage too, it’s €50 but worth every cent.