Rescue me! Maple leaves withering and turning black
(Sorry: I posted this first in the gallery because I thought I could only attach pictures there; but I've attached links to the pictures here).
Some friends of mine left me a bunch of their plants when they moved, including two young Japanese maples in pots. One is a Bloodgood (it still has the label) but I don't know what the other is. The mystery maple is the one with the problem.
A couple of weeks ago the leaves started to sprout and it was looking great--bright green leaves with a slightly reddish border. Then suddenly some of the leaves started to wither and turn an ashen black.
Is this a disease, a parasite, or something I did wrong? (I am very new to any sort of gardening)
Could it be from too much water? We had very heavy rains last weekend (3 inches in 3 days). Before that there was drought (although I'd been watering it). It's also been a bit cold here the past few nights (but above freezing) and very hot before that (highs in the 90s). Could the pot be too small?
If it's a disease/parasite, will it spread to the other maple (which is on the other side of the house) or the other plants? Is there anything I can do to save it?
I will try to attach pictures, but I apoloize in advance; I took them at night.