looks like second gear clutches are going out. is probable that the intermediate clutches are going bad as well as the forward ones. I think this not what you wanna hear but I think is time for an overhaul.
we could consider that the fluid was low but that will affect in all gears, a shift solenoid will make it not going in to the gear or will not disengage.
I hope this is of some help for you and if you have any more questions let me know.