Strange Danio Behaviour

Evening all,
Hopefully a bit of advise will put my mind at rest and confirm that there is nothing wrong.

50ltr tank, set up 4 months, internal filter, Ammonia 0ppm, Nitrite, 0ppm, nitrate 20-25ppm, PH 7.5-8 plastic and live plants, 24 degrees water, 3 leopard danio, 3 zebra danio, 3 glowlight tetra. (stats taken half hour ago)

All of the fish live in harmony and there is never any problems. The danios chase each other now and then but nothing to serious. I believe that I have at least 3 female danios maybe even 4. Over the last hour I noticed that all 6 of the danios were together around a plant in the corner. what I believe to be a  female was surrounded by the 5 others. The danio in question does have a large belly and may be ready to drop eggs. I have never seen this before in them and would like some feedback that there are no problems and it is just because the female is about to spawn. The glowlight tetras just do their thing and are not interested in the activity. Just a little disconcerting to see them behaving so differently.

Look forward to replies and any questions please fire away

Thanks Jay