It is okay to use 6JE6, 6JE6A, and 6JE6B in your amp, however the 6JE6 has lower plate dissipation than the 6JE6A and 6JE6B. Meaning, you won't get as much output from the 6JE6, nor can you put as much input drive into a 6JE6. A 6JE6 has 24-25W plate dissipation. If you have 6JE6A's and 6JE6B's, use those. They are rated the same as a 6LQ6/6JE6C, at 30W plate dissipation per tube. 6JE6A's and 6JE6B's are basically just shorter versions of the 6LQ6.
~Cheers~