I've seen MUCH worse. If the redness of the petioles is visible from the top of the leaf, as reddening VEINS, you really need to worry, but actually your plant doesn't look bad to me.
You can get all sorts of stuff online... make sure whatever you get has micronutrients in it. The cactus stuff is interesting because cacti are one of the few classes of plants that require virtually NO nitrogen from the soil for growth! So cactus nutes are good for bloom! Mg probs... can't tell without seeing the leaf surface.