I have 500-800 kB/s syncing from a raspberry pi 2 to a raspberry pi 1 (both with encrypted data partitions, partition where the index of syncthing is not) so your ~200 kB/s sounds wrong if your devices are not even more underpowered, leave the GUI closed (check speed with another tool) and wait for some minutes.
At the beginning sync is always slower for me (100 kB/s maybe), but after a while it gets faster. Probably it is slow while the receiving device still processes the index and as soon as it is done it gets faster.