It is certainly understandable to be emotionally and financially attached to the trees after a decade but it is time for them to go. In Texas it can take 20-30 years for susceptible pin and shumard oaks to show chlorosis so it's not unheard of. That said I have NEVER seen a tree have chlorosis as bad as your examples. Go ahead and try a couple things, watch it fail or make a insignificant improvement, come to terms with the reality of situation and get rid of em. Or save yourself some time and money and get rid of them. Up to you of course and I am seldom this bullish on anything really, but this is one time I really have to stand my ground with my opinion. I

I posterd this reply a couple of days ago i thought ...guess it didn't take .. I also thought it was a sugar maple ...and they really arn't effected by much in my experience ...Spruce may be right about "maple decline" I had not heard of that ..sounds like a generic name for something effecting them not yet diagnosed ..but I have not seen that here on any sugar but it may be in other areas . I had two thoughts on this #1 try to contact the former owner and see if this is something going on for a while or ask a neighbor that will tell you alot ..it may do this every spring and then put on some growtrh during summer ( I have had seveal pin oaks do this from lack of acidity in the soil but never seen that in a sugar maple but it is possible although it probabaly wouldn't be the same acididy problem but something in the soil type "area" area) ...that doesn't tell you its "ok" but may help in the diagnosis..#2 my first instinct is something in the soil like septic chemicals...something the roots have gotten into or someting sprayed on it in early spring ( less likely) ..do you live in the country?? I would bet it is a soil thing one way or another...anyway I had stated in my original post also that you have the extension service or a good tree person come out and look at it...there are several possibilities that photos won't help in diagnosis and it must be personally inspected ..David

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Don't know if it happens so much with JMs but with some trees,when multiple branches/trunks grow surrounding one in the middle,the central one often dies off as it gets harder to keep it supplied with nutrients etc.as the other branches grow.The other trunks have overtaken the central one so maybe it was gonna happen one day anyway.I expect the stump is dead now so wouldn't worry too much about dark patches. Not sure about the green stuff,could it be just harmless lichen?One of the resident experts will be along to throw light on the whole situation I'm sure :) As for the seedlings,just dig'em up carefully when big enough to handle and plant in a free draining container and position in a sheltered spot 'til bigger.