African Dwarf frog sick, would like some expertise on what is wrong...

[bloopton]

My little african dwarf frog (who I raised form a tadpole, along with 5 siblings) has been doing fine, behaving normally, eating, etc. there is a problem though. His front fin is slightly red, and I noticed that one of his "fingers" is missing!!! I keep watch over the frogs each day, ive noticed the redness for 2 days, and changed the filter/water accordingly. I've isolated the frog, put in some substrate and a tiny plant. Please help!

Here are some pics of the poor little guy: (problem is with his left arm)

[LilyPad]

Is there something in the tank he could have gotten caught on?

[bloopton]

No, the only thing in the tank is an elodea plant, tiny round/smooth substrate, and a rubbery/squishy (no edges) fake plant that they hide in. Is the redness indicative of something? I just dont want the little guy to loose his hand... its hard watching him without his middle part of his fin, although he doesnt show any changes in behavior.