@cldsmit
I've had that happen before. When that happens, you need to harvest them again and attempt to identify. The plants in the sim's inventory should say they are unidentified at that point. Another thing I have found is that if you look at all the plants in a stack, you might find most of them have been identified but there may be a few in that stack that still say unidentified. Identifying those will usually complete the milestone for that plant. It sounds like you have 2 so you'll have to figure out which ones they are. Check your collectibles to see if all of them show up there and if not then you'll be able to see what is missing (assuming you are playing a solo sim).
And if you haven't figured it out yet, the only time of year when all 10 plants are available and will grow at the same time is Summer. Some of them will be dirt piles during the rest of the year.
Hope this helps.